1. Field of the Invention
The present invention relates to an alignment assembly and a method of alignment using said assembly to determine or establish an angle between a tool mounting assembly, such as a rotatable chuck and a flat surface, such as the work surface of a machine tool assembly.
2. Description of the Relevant Art
In the daily practice of using a machine tool for machining mechanical components there arises the necessity for adjusting the tool mounting assembly of the machine tool through various angles in order to facilitate the proper cutting and shaping of the material being machined. It is often necessary to adjust the angular alignment of the machine tool to high precision. After work is accomplished at these various angles it is desirable to restore the tool mounting assembly to an angle perpendicular to the working surface of the machine tool, and to do so with a high degree of accuracy. In the present situation a skilled craftsman must spend a great deal of time and labor using various tools such as squares, sine bars, dial indicators and the like to properly position the tool mounting assembly. The situation is further complicated in that the clamping mechanism used to hold the tool mounting assembly securely in the desired position can alter its position in an irregular manner while it is being tightened thus requiring that the craftsman anticipate the movement of the assembly during the tightening and adjustment procedure. Often the result is that repeated trial and error attempts must be made to align the machine tool within acceptable tolerances. It is therefore obvious to one familiar with the present art that this is a time consuming and inefficient procedure both in regard to the overall cost of manufacturing and labor and also the required tedium on the part of the craftsman.
In the past, efforts to achieve such angular alignment with the work surface has involved the use of an alignment device of the type described in U.S. Pat. No. 4,437,803 issued Mar. 20, 1984. This patent pertains to an apparatus for squaring the spindle or tool holding assembly with respect to the work surface of the milling machine by utilizing a cylinder or shaft inserted into the tool holding assembly. The lower portion of the shaft extends into a second cylindrical member and moves freely within the second cylinder. The second cylinder in turn pivots in perpendicular orientation to the axis of the shaft on a third member of the device forming a frame. The frame makes contact with the work surface utilizing at least two contact points and supports an indicator which makes contact with the second cylinder and quantizes the position of the lower portion of the shaft during the alignment procedure relative to the frame which is staying in parallel orientation with the work surface by virtue of the points of the frame in contact with it. Squareness or perpendicularity of the tool holding assembly is established by adjusting the tilt of the tool holding assembly until the indicator shows a predetermined position to indicate perpendicularity. An alternative embodiment of the device makes this procedure simpler by arranging an indicator with two dials which facilitate making comparative measurements by indicating the direction of tilt of the tool holding assembly and by increasing the sensitivity of indication by making the two dials line-up with each other in the position of perpendicularity. However, such a device still requires skill and time on the part of the user for precise squaring of the tool holding assembly and is not useful for establishing alignment at angles other than the one at perpendicularity for reasons which will become obvious with further explanation.
The prior art concern is intended for establishing the perpendicularity of the tool holding assembly and makes use of indicators and apparatus which are only useful for this purpose. If one tried to align the tool holding assembly at 5 degrees, for example, readings by the indicator would no longer be accurate or meaningful for the purpose of quantitatively determining an angle. First, an error is introduced in the displacement of the indicator because the actual displacement quantized by the indicator is the tangent of 5 degrees multiplied by the length of shaft between the pivot point of the second member and the point of contact of the indicator in the perpendicular position. At the same time a second error is introduced at the contact point of the indicator with the second member of the device because the point of contact is always changing as the angle of the shaft changes, and depending on the geometry of the tip of the indicator the error introduced can be quite complex. For example, if the tip of the indicator is rounded or in contact with a radial surface of the second member, as in the alternative embodiment of the above noted prior art, the error introduced would make the actual angle of inclination of the chuck difficult, if not impossible, to determine. A third and more obvious error is introduced by the indicator itself since its purpose is to determine perpendicularity and to quantize displacement to the right or left of perpendicularity. The equally spaced intervals or other indicia of the indicator serve only to show whether this tilt is small or great. Thus the dial display of such on indicator cannot convert to meaningful output in degrees of angle away from perpendicularity. Furthermore, the prior art of reference makes no mention of measuring or quantizing angles other than perpendicularity. Rather, it is the perpendicularity which is quantified by the indicator, and the making on its face, by merely showing the direction, clockwise or counter-clockwise, which the tool holding assembly is out of perpendicular alignment. It is obvious, therefore, that the above mentioned prior art is unsuitable for alignment at angles away from the one perpendicular to the work surface and was never intended to do so.